// 默认shadow
@mixin box-shadow($size: 20px, $color: #1989fa7a) {
  -webkit-box-shadow: 0 0 $size $color;
  -moz-box-shadow: 0 0 $size $color;
  box-shadow: 0 0 $size $color;
}
@mixin font-title($size: 30px, $weight:700, $location:center, $color:black) {
  font-weight: $weight;
  text-align: $location;
  font-size: $size;
  color: $color;
}